1. Field of the Invention
The present invention relates to a wafer processing method including the steps of grinding the back side of a wafer and next forming a through electrode connected to an electrode of each device formed on the front side of the wafer from the back side of the wafer.
2. Description of the Related Art
A plurality of devices such as ICs and LSIs are formed on the front side of a semiconductor wafer so as to be partitioned by a plurality of crossing division lines. The semiconductor wafer is divided into the individual devices by a dicing apparatus, and these devices divided from each other are widely used in various electrical equipment such as a mobile phone and a personal computer.
In recent semiconductor device technology, a stacked semiconductor package such that a plurality of semiconductor chips are stacked is effectively used in achieving a higher density and a reduction in size and thickness. In this semiconductor device technology, the back side of a wafer is ground by abrasive members to reduce the thickness of the wafer to about 50 μm, and thereafter a through electrode is formed from the back side of the wafer so as to be connected to an electrode of each device formed on the front side of the wafer. Accordingly, before grinding the back side of the wafer, a reinforcing plate is attached through a bond to the front side of the wafer.
However, in forming the through electrode connected to the electrode of each device, the wafer is exposed to an environment of relatively high temperature. Accordingly, an epoxy bond having a strength of enduring a high temperature of 250° C. is used as the bond for attaching the reinforcing plate to the front side of the wafer. Thus, the bond has a strength of enduring a high temperature of 250° C. Accordingly, in removing the reinforcing plate from the front side of the wafer, the reinforcing plate is heated to raise the temperature of the bond to greater than 250° C., and the reinforcing plate is slid on the front side of the wafer and removed therefrom without applying a load to the wafer.